Snap-closing gas lift valve



Dec. 21, 1965 M. M. LILLY SNAP-CLOSING GAS LIFT VALVE 2 Sheets-Sheet 1 Filed Aug. 5, 1963 MOJ 0/? M Z //5 INVENTOR.

Dec. 21, 1965 M. M. LILLY 5 SNAP-CLOSING GAS LIFT VALVE Filed Aug. 5, 1963 2 Sheets-Sheet 2 MaJon M A/// g INVENTOR.

ATTORNEY United States Patent Oil ice 3,224,459 Patented Dec. 21, 1965 3,224,459 SNA?-CLOSIN G GAS LIFT VALVE Mason M. Lilly, Harold Brown (10., P.O. Box 25047, Houston, Tex. Filed Aug. 5, 1963, Ser. No. 299,822 5 Eiaims. (Cl. 137-155) This application is a continuation-in-part of my co pending application Serial No. 298,943, filed July 31, 1963, now abandoned.

This invention relates to gas lift valves and more particularly to gas lift valves having snap-closing features.

Gas lift valves of the conventional types, particularly those which load the valve with gas pressure-charged bellows, have an inherent characteristic which is detrimental both to its function and to the life of its operating parts. The bellows, which is primarily a sealing member, also acts as a spring. In addition, the gas charge in the pressure dome contributes some spring eflFect which must be overcome in operation of the valve. As the valve closes, the springs put up increasing resistance to closing, requiring increased force to complete the closing. The closing force is provided only by a reduction in the external gas pressure in the well casing surrounding the valve. However, as the valve is pinched oil, it becomes progressively more difficult to lower the casing gas pressure which must escape through the valve. Ultimately, the valve closes because throttling through the valve seat reduces the pressure downstream sufficiently to overcome the final spring force.

This action may be shown by the following example:

Assuming a gas lift valve with- To find opening pressure:

PbAb=Pc(AbAv) +Pt(A1)) Pc=700(.30) 5G0(.049) 212.4

Where Pc=opening pressure.

=741 p.s.i.

Thus, when the casing pressure has built up to 741 p.s.i.,

the valve will open. The area of the seat will be exposed to this additional 241 p.s.i. (i.e. 741 minus 500). This provides 24-1 0.049 or an additional 11.8 lbs. to open the valve. Since the valve operates against a spring bellows having a rate of 150 lbs./in., the valve will open approximately 0.080 in.

The valve will close when the casing pressure has been reduced to the dome charge or 700 p.s.i. This does not mean that the valve will remain open 0.080 in. throughout the open period. Quite the contrary, the valve will close proportionately to the reduction of the casing pressure, in this case, 0.002 in. for each pounds Per square inch reduction.

Accordingly, it is a primary object of this invention to provide a means for overcoming this throttling action so as to maintain the valve fully open or very nearly so, until the casing pressure has been reduced sufiiciently to insure tight snap-action closure.

An important object is to provide a means to assure snap closing of the valve through the terminal portion of its closing movement, that is, from about the final fully open position to a fully closed position.

A more specific object is the provision of a valve control mechanism for assuring snap closing of the valve seat,

7 said control mechanism comprising a Belleville spring.

O taining the lifting gas under pressure.

Belleville springs are well known, widely used springs which are constructed in the form of accurately dimensioned coned (frusto-conical) washers. 'By selection of dimensions, primarily height and thickness of the washer material, various load-deflection characteristics can be obtained. If the ratio of the height or depth of coning h to the thickness t of the washer material is in the proper range, the spring has a very useful quality. During the first third of its useful stroke, load increases rapidly with deflection to a maximum value. During the remainder of the stroke, the load falls from the peak to some minimum value which may be Zero. When the applied load falls below the minimum value, the spring will return to its original position.

Accordingly, it can be readily seen from the example given above that with the valve closed to a position of 0.040 in. from its seat, a casing pressure reduction of 20 p.s.i. is required to close the valve.

Based on the 0.030 sq. in. bellows area, this amounts to a force of 6 lbs.

Therefore, if a Belleville washer, having a maximum load at least 6 lbs. above its minimum after a stroke of at least, for example, 0.040 in., is positioned in a valve so that it is contacted in the last 0.060 in. of itss troke, then the operation of the valve in closing is improved immensely. The valve will close normally until the washer is contacted. The closing will be slowed down (since additional force is required to load the washer to its peak). When the peak is reached, the loading force will fall off rapidly, allowing the valve to trigger or snap closed, with little or no additional force.

The attached graph (FIG. 4), based on the foregoing example, shows the casing pressure reduction necessary to operate the bellows alone, the Belleville washer alone, and the combination of the two. It can readily be seen that by the time the valve is 0.040 in. from the seat, the casing pressure will have been reduced sufficiently to close the valve spontaneously through the terminal portion of it movement.

The objects and advantages of this invention will become more fully apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates a useful embodiment in accordance with this invention.

In the drawing:

' FIG. 1 is a longitudinal, partly sectional view showing a gas lift valve in accordance with this invention mounted for operation on a well tubing and showing the valve in fully open position;

FIG. 2. is a fragmentary view similar to FIG. 1, showing the valve moved partly toward the closed position;

FIG. 3 is a view similar to FIG. 2 showing the valve in the fully closed position; and

FIG. 4 is a graph illustrative of the spring charcteristics of the Belleville spring alone, the bellows alone, and the combination of the Belleville spring and bellows.

Referring to the drawing and FIGS. 1 to 3, inclusive, there is shown a generally conventional gas lift valve of the casing pressure-operated type. In this type of valve the bellows area is subjected to the dominant casing pressure and the valve seat beneath the valve to the tubing pressure. The valve comprises a tubular housing 10 provided with a threaded pin 11 at its lower end for reception in the socket 12 of a valve lug 13 mounted on the exterior of a well tubing T and having a passageway 15 communicating the bottom of socket 12 with a port 16 in the wall of tubing T. It will be understood that tubing T and the valve will be surrounded by a well casing C con- Body 10 is provided with an annular restriction 17 intermediate its ends having an axial passage 18 therethrough. Restriction 17 divides the interior of body into an upper pressure dome 19 and a lower bellows chamber 20. The latter is provided adjacent its lower end with a plurality of ports 21 through which pressure fluid exteriorly of the valve and tubing in casing C may enter the interior of bellows chamber 20. The bottom of bellows chamber is provided with an axial passage 22 communicating with the bottom of socket 12, and thence with passage 15. The inner end of passage 22 communicating with the interior of bellows chamber 20 is formed to provide a valve seat 23. A valve 24 of generally hemispherical form is mounted on a valve stem 25 for reciprocation relative to valve seat 23. A flexible bellows 26 surrounds valve stem 25 and has its lower end sealingly secured at 27 to a shoulder 28 formed on stem 25. The upper end of bellows 26 is sealingly secured at 29 to an internal shoulder 30 formed by a reduced diameter bore 31 provided interiorly of bellows chamber 20. The interior of bellows 26 is thus placed in pressure communication with pressure dome 19 through passage 18 and bore 31. Passage 18 is smaller in diameter than bore 31 and provides a downwardly facing shoulder 32 which limits the upward movement of stem 25, the upper end of which has a free sliding fit in bore 31. A stud 33 provided at its upper end with an enlarged head 34 extends through passage 18 and is screwed into a threaded socket 35 provided in the upper end of stem 25. Head 34 being larger in diameter than screw 33 provides the downwardly facing annular shoulder 36. Surrounding screw 33 and seated on a shoulder 37 defined by the upper end of restriction 17, is a Belleville spring washer 38 having an axial opening 39 smaller in diameter than shoulder 36 and positioned with its apex extending upwardly. A spacer ring 40 having an axial bore 41 is positioned about screw 33 immediately above and resting in contact with the apex of washer 38.

The upper end of body 10 is provided with an axial passage 42 communicating with pressure dome 19 and fitted with a check valve 43 of conventional design through which loading gas may be introduced into pressure dome 19 and held therein. Passage 42 communicates with a counterbore 44 leading to the upper end of body 10 and a threaded plug 45 is screwed into counterbore 44 to additionally seal off against leakage to or from the pressure dome.

Operation of the device is as follows: It will be assumed that the external or casing pressure has increased to some value exceeding the pressure loading on valve 24, so that the valve is in the fully open position as illustrated in FIG. 1. In this position, it will be noted that screw 33 has been adjusted so that shoulder 36 will be spaced a short distance from the upper end of spacer ring 40.

With the valve in the open position, pressure gas from the interior of casing C will flow through port 21, seat 23,

' and thence via passages 22 and 15 through port 16 into the interior of tubing T to perform its function of lifting the fluid column in tubing T. As the gas from the casing flows into the tubing the pressure in the casing will fall proportionately. When the pressure falls to a point below the closing pressure of the valve, the valve will move downwardly toward seat 23 until shoulder 36 engages the upper end of spacer ring 40 and begins to exert downward pressure therethrough on Belleville washer 38, as seen in FIG. 2. The position of screw 33 in stem 25 will have been adjusted so that when the initial engagement of the shoulder 36 with ring 40 occurs, valve 34 will have moved to a position such that the full capacity of the port in seat 23 will still be available, that is, the valve will still be fully open so far as volumetric discharge capacity is concerned. As the casing pressure continues to drop, pressure will be exerted through shoulder 36 and ring 40 on the Belleville washer causing deflection of the same in proportion to the pressure reduction. When the loading thus applied to the Belleville washer has attained a pre-determined value, depending upon the dimensions of the washer, as will be described hereinafter, the loading will pass through the maximum load value of the washer and cause sudden collapse of the washer, as illustrated in FIG. 3, permitting the valve to move rapidly through the terminal portion of its travel to the fully closed position. Thus moving the valve through the terminal portion of its travel from a fully open position to a fully closed position by a rapid snap action avoids the throttling action common to more conventional casing pressure-operated valves of the general form herein illustrated. By thus avoiding throttling action and providing for snap closing, many of the difliculties, particularly erosion and excessive loss of pressure gas, will be avoided.

To provide the desired action, the Belleville spring washer will be selected to have pre-determined deflection characteristics. As noted previously, the desired characteristics will be determined by the ratio of the depth of coming or height h to the washer thickness 1. This is a well known relationship and washers of any desired h/ t ratio may be obtained commercially.

In general, it has been found that a Belleville washer having an h/ t ratio in the range of about 1.6 to about 2.8

will provide the characteristics most desirable for providing the desired snap action in valves of the kind herein described.

FIG. 4, as noted previously, is a graph showing the characteristics of the washer alone, the bellows alone, and the combination of the two in the example set forth above. The distance to close the valve in each instance is plotted against the casing pressure draw-down from fully open to closed in pounds per square inch. It will be seen from the graph that the closing movement of the bellows alone is a straight line, being a linear function of the pressure reduction. The Belleville spring passes through a point of peak loading and then drops more or less sharply in proportion to the continued decrease in casing pressure. The graph of the combination of the two shows that when the load has attained the peak, closing occurs with very small further reduction in pressure, thereby effecting the snap closing through the terminal portion of the closing movement of the valve. In this illustration, the terminal closing movement encompasses about half the total closing movement.

From the foregoing, it will be seen that unlike conventional applications, this invention makes use of the collapsing characteristics of Belleville springs to effect the snap action sought in gas lift valves.

It will be understood that various modifications and changes may be made in the details of the illustrative embodiment within the scope of the appended claims without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A gas lift valve, comprising, a generally tubular housing, a valve seat port in the housing, a valve member reciprocable relative to the port for controlling the same, an elongate stem secured to the valve member, annular abutment means in the housing having an axial opening through which the stem is reciprocable, annular shoulder means carried on said stern for longitudinal movement therewith relative to said abutment means, resilient means biasing the valve member toward the port-closing position, and a snap-acting mechanism for controlling the closing movement of the valve. member comprising, a Belleville spring washer seated on said abutment means surrounding said stem in longitudinally spaced relation to said shoulder means, the spacing being such as to permit initial limited free longitudinal movement of the stem in the port-closing direction followed by engagement of the washer by said shoulder means whereby to resist further movement of said stem throughout at least a portion preceding the terminal portion of said move ment, said washer having a pre-selected h/t ratio, as hereinabove defined, such that when the deflection of said washer under the closing pressure of said biasing means exceeds a pre-determined fraction of h, the washer will 5 6 collapse allowing the valve member to snap through said port from fully opened position to said port-closing terminal portion to the port-closing position. position.

2. In a gas lift valve according to claim 1, said resilient biasing means comprising a gas-charged flexible bellows. References Cited by the Examiner 3. In a gas lift valve according to claim 2, said h/t ratio 5 UNITED STATES PATENTS being in the range Of about 1.6 "L0 about 2.8. 2 51 319 9 1953 Cummings 137 155 fl. In a gas lift valve according to claim 3, said fraction 2,652,857 9/1953 Engstmm 251 75 bemg at least f 2,668,553 2/1954 Howard 137 155 5. In a gas 11ft valve according to cla1m 1, said terminal 3,099,282 7 /1963 Mina. 251 75 XR portion being at least the minimum lineal distance re- 10 quired to move said valve member relative to said seat ISADOR WEIL, Primary Examiner- 

1. A GAS LIFT VALVE, COMPRISING, A GENERALLY TUBULAR HOUSING, A VALVE SEAT PORT IN THE HOUSING, A VALVE MEMBER RECIPROCABLE RELATIVE TO THE PORT FOR CONTROLLING THE SAME, AN ELONGATE STEM SECURED TO THE VALVE MEMBER, ANNULAR ABUTMENT MEANS IN THE HOUSING HAVING AN AXIAL OPENING THROUGH WHICH THE STEM IS RECIPROCABLE, ANNULAR SHOULDER MEANS CARRIED ON SAID STEM FOR LONGITUDINAL MOVEMENT THEREWITH RELATIVE TO SAID ABUTMENT MEANS, RESILIENT MEANS BIASING THE VALVE MEMBER TOWARD THE PORT-CLOSING POSITION, AND A SNAP-ACTING MECHANISM FOR CONTROLLING THE CLOSING MOVEMENT OF THE VALVE MEMBER COMPRISING,A BELLEVILLE SPRING WASHER SEATED ON SAID ABUTMENT MEANS SURROUNDING SAID STEM IN LONGITUDINALLY SPACED RELATION TO SAID SHOULDER MEANS, THE SPACING BEING SUCH AS TO PERMIT INITIAL LIMITED FREE LONGITUDINAL MOVEMENT OF THE STEM IN THE PORT-CLOSING DIRECTION FOLLOWED BY ENGAGEMENT OF THE WASHER BY SAID SHOULDER MEANS WHEREBY TO RESIST FURTHER MOVEMENT OF SAID STEM THROUGHOUT AT LEAST A PORTION PRECEDING THE TERMINAL PORTION OF SAID MOVEMENT, SAID WASHER HAVING A PRE-SELECTED H/T RATIO, AS HEREINABOVE DEFINED, SUCH THAT WHEN THE DEFLECTION OF SAID WASHER UNDER THE CLOSING PRESSURE OF SAID BIASING MEANS EXCEEDS A PRE-DETERMINED FRACTION OF H, THE WASHER WILL COLLAPSE ALLOWING THE VALVE MEMBER TO SNAP THROUGH SAID TERMINAL PORTION TO THE PORT-CLOSING POSITION. 